1. Field of the Invention
The present invention relates to vehicle suspension systems. More particularly, the present invention relates to the structure and installation of a stabilizer bar for a vehicle suspension system.
2. Description of the Background Art
A structure in which a stabilizer bar is provided in a wishbone-type suspension system between right and left upper suspension arms is known. For example, such a suspension system is described in Japanese Patent Laid-open No. Hei 3-213414.
FIG. 2 of Japanese Patent Laid-open No. Hei 3-213414 has been reproduced herein as FIG. 8. It will be described using newly assigned reference numerals. FIG. 8 is an explanatory diagram showing a conventional structure of a stabilizer bar within a suspension system of a vehicle. An upper suspension arm 202 and a lower suspension arm 203 are attached to a frame 201 so as to be pivotal in the vertical direction. A knuckle 204 is attached to the tips of the upper suspension arm 202 and the lower suspension arm 203, a wheel 206 is rotatably attached to the knuckle 204, and a stabilizer 208 is attached to the right and left upper suspension arms 202 and 202 (only one upper suspension arm 202 is shown) via joints 207 and 207 (only one of the joints 207 is shown).
A disadvantage of this conventional system becomes apparent when the vehicle body rolls. In this situation, a stroke difference occurs in the vertical direction between the right and left wheels 206, with the result that the stabilizer 208 is twisted since a vertical swing amount of the right upper suspension arm 202 and that of the left upper suspension arm 202 are different from each other. Consequently, a large load acts on the upper suspension arms 202. To support the load, the upper suspension arms 202 need high rigidity. In particular, a portion of the upper suspension arm 202 to which the joint 207 is attached has to have a large sectional area to increase rigidity, or has to be reinforced.
When an attachment part for attaching the stabilizer 208 is provided for the upper suspension arm 202, and an attachment part for attaching a rigid body 211, which is provided between the upper suspension arm 202 and the lower suspension arm 203, is provided for the upper suspension arm 202, the shape of the upper suspension arm 202 becomes complicated and the cost increases. Further, the shape of the upper suspension arm 202 is limited by these requirements so that the flexibility of designing deteriorates.